This invention relates to a method of making a hose coupling and, more particularly, to a method wherein the outer element is provided by cold forming, i.e, drawing, rather than machining.
The coupling for the end of a flexible hose normally has included an insert body of fairly rigid, tubular construction inserted within a hose end, and a deformable sleeve having interior serrations which is crimped or swaged, i.e., radially inwardly deformed, into clamping relation with the hose. Normally, the outer element or sleeve is manufactured by machining coupling shells from round or hexagonal bar stock or from tubing on turret lathes and screw machines. The disadvantage of this method is the time and scrap involved in machining the shells. However, no one has departed substantially from this technique because of the feeling that the serrations or tangs in the interior of the sleeve had to face downstream, i.e., oppose the direction of hose movement tending to separate the hose from the coupling. We have discovered, however, that an entirely satisfactory coupling can be obtained with the tangs developed upon swaging facing "upstream" so that now it is possible, for the first time, to dispense with the expensive machining operation and instead develop the deformable sleeve by cold forming, i.e., drawing.
More particularly, the invention contemplates the cold forming to develop a generally frusto-conical sleeve having at least one circular discontinuity in the interior wall thereof. This can be characterized by a step in the interior wall defined by the intersection of an axially extending wall portion and a radially extending wall portion. This, upon swaging or the like, develops an advantageously powerful compressive action on the hose which results in a firm union between the coupling and the hose itself.
The efforts of the prior art stopped far short of the instant invention. For example, in Shaw U.S. Pat. No. 2,685,458, the essential teaching is to a ferrule including serrations in the inner surface thereof formed by casting and machining. However, Shaw discloses that in instances it can be an advantage to use a drawn ferrule which is subsequently subjected to crimping but in such a case the serrations extend longitudinally rather than being radially disposed. Miller U.S. Pat. No. 2,211,147 also teaches longitudinally extending serrations in a shell formed in a cold forming process.
Goward et al U.S. Pat. No. 3,838,592, discloses a hose end fitting wherein a ferrule includes serrations formed on the outer surface but again are oriented so as to follow the prior teaching of having the tang like aspect directed downstream.
Other objects and advantages of the invention may be seen in the details of construction and operation set down in the ensuing specification.